The objective of this investigation is to obtain an improved understanding of the underlying biomechanics associated with total knee replacement design. The methodology is divided into three areas: experimental observation of net knee joint kinematics and kinetics; analytical determination of internal force distributions at the knee; and stress analysis of implanted prosthetic components. The three areas of study will be integrated as follows. Data generated on net joint reactions will be used as input to a model for internal force calculations. Internal force distribution will then be input to the stress analysis models. The basic questions addressed in this study will include the following: 1. The relationship between patient variables and prosthetic design criteria. 2. The extent to which patient knee mechanics varies among groups treated with different knee replacement designs and normals. 3. The minimum mechanical requirements for prosthetic component design. 4. The minimum mechanical requirements for an interface free from potential loosening. It is intended that findings resulting from this study will aid in improved usage and design of total knee replacements.